Method and apparatus using hydrogen peroxide and microwave system for slurries treatment

ABSTRACT

A method and apparatus for treating slurries of organic solids is disclosed. A slurry of organic solids is admixed with hydrogen peroxide, followed by exposure to microwave irradiation resulting in the heating of the mixture and enhanced hydrolysis of the organic solids. The treated slurry of organic solids can then be further treated in a variety of downstream processes, including solid separation, digestion and fermentation. The supernatant portion of the treated slurry of organic solids can be a source from which to recover compounds such as nutrients (for example nitrogen, phosphate, potassium, magnesium, calcium) or industrial organic compounds (such as acetic acid, propionic acid, butyric acid), or as a source of readily biodegradable organic compounds for supplementing a biological wastewater treatment process, digester or fermenter.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of pending U.S. patent application Ser.No. 12/376,934 filed 19 Mar. 2009, and claims the benefit of PCT patentapplication No. PCT/CA2006/001327 filed 11 Aug. 2006, published as WO2008/017137 on 14 Feb. 2008. The disclosure of each of the previouslyreferenced patent applications is hereby incorporated by reference inits entirety.

TECHNICAL FIELD

The present invention relates in general to the treatment of organicwaste material, such as sludge resulting from sewage treatmentfacilities, animal waste, or industrial organic waste. Morespecifically, the invention relates to a process and apparatus fortreating organic waste materials by the combination of microwaveirradiation and oxidants such as hydrogen peroxide or ozone as a form ofadvanced oxidation process (AOP). The invention functions to solubilizeorganic solids through hydrolysis, resulting in soluble compoundsavailable for recovery or further processing, as well as providingmicrobicidal activity, breaking down organic molecules, and reducing themass of residual solid matter.

BACKGROUND

The disposal of organic waste materials such as sewage sludge, animalmanure, food processing waste, and the like, presents both environmentand public health concerns.

The production of large volumes of sludge as an end-product fromwastewater treatment processes poses one of the biggest challenges tothe wastewater treatment industry. The handling and disposal of sludgeresiduals has significant social, environmental, and economicimplications. Treatment and disposal of sewage sludge from wastewatertreatment plants can account for over half of the total cost ofwastewater treatment plant construction and operation. Currently,residual sludge is commonly digested, incinerated, deposited inlandfills, or used as fertilizer through agricultural land applicationof the residual biosolids.

In current wastewater treatment processes, toxic heavy metals becomeconcentrated in the residual sludge. There may also be dangerous levelspathogenic organisms present in the residuals. For these reasons thereare increasing concerns that land application of sludge residuals may beharmful to the environment and to public health. Under such social,environmental and economic pressures, significant effort has beeninvested in developing new methods of treating wastewater and wastewatersludges that result in smaller amounts of residual requiring disposal.

Anaerobic digestion is a very common solids reduction and stabilizationtechnology, but is relatively inefficient due to the lowbiodegradability of the sludge. This poor biodegradability isparticularly evident in the case of digesting secondary or wasteactivated sludge. The benefit of anaerobic digestion is that themethanogenesis stage of the process results in the production of methane(biogas) which can be used as an energy source. To improve theefficiency of the anaerobic digestion process, many techniques whichenhance the biodegradability of these sludges have been developed inrecent years.

The anaerobic degradation of particulate organics is considered to be asequence of three steps: hydrolysis, acidogenesis, and methanogenesis.Among these, biological hydrolysis of the particulate organics has beenconsidered to be the rate limiting step.

Many of the techniques recently developed to improve thebiodegradability of sludges therefore focus on improving hydrolysis byother means. The processes most focused on are chemical oxidationdisintegration by ozone, mechanical disintegration by various methods,and thermal or thermal/chemical disintegration. These techniques includethose discussed in the following references:

-   -   Ahn, K.-H., Park, K. Y., Maeng, S. K., Hwang, J. H., Lee, J. W.,        Song, K. G. and Choi, S. (2002). Ozonation of wastewater and        ozonation for recycling. Wat. Sci. Tech., 46(10), 71-77.    -   Chiu, Y. C., Chang, C. N., Lim, J. G. and Huang, S. J. (1997).        Alkaline and ultrasonic pre-treatment of sludge before anaerobic        digestion. Wat. Sci. Tech., 36(11), 155-162.    -   Hiraoka, M., Takeda, N., Sakai, S. and Yasuda, A. (1984). Highly        efficient anaerobic digestion with thermal pre-treatment. Wat.        Sci. Tech., 17(4/5), 529-539.    -   Kepp, U., Machenbach, I., Weisz, N. and Solheim, O. E. (2000).        Enhanced stabilisation of sewage sludge through thermal        hydrolysis—three years experience with full scale plant. Wat.        Sci. Tech., 42(9), 89-96.    -   Recktenwald, M. and Karlsson, I. (2003). Recovery of wastewater        sludge components by acid hydrolysis. Presented at IWA        Specialised Conf. BIOSOLIDS 2003 Wastewater Sludge as a        Resource, Trondheim, Norway, 23-25 Jun. 2003.    -   Svanström, M., Modell, M. and Tester, J. (2004). Direct energy        recovery from primary and secondary sludges by supercritical        water oxidation. Wat. Sci. Tech., 49(10), 201-208.    -   Tiehm, A., Nickel, K., Zellhorn, M. and Neis, U. (2001).        Ultrasonic waste activated sludge disintegration for improving        anaerobic stabilization. Water Research, 35, 2003-2009.    -   Weisz, N., Kepp, U., Norli, M., Panter, K. and Solheim, O. E.        (2000). Sludge disintegration with thermal hydrolysis—cases from        Norway, Denmark and United Kingdom. 1st IWA World Congress,        Paris 3-7 July. Pre-prints Book 4, pp 288-295.    -   Yasui, H. and Shibata, M. (1994). An innovative approach to        reduce excess sludge production in the activated sludge process.        Wat. Sci. Tech., 30(9), 11-20.

Most of these prior processes operate either with large amount ofchemical dosage or under high temperature and pressure conditions orboth. Energy consumptions are typically large for many of theseprocesses.

There remains a need for a cost-effective process to achieve solid wastedisintegration, nutrient solubilization and pathogen destruction.

The foregoing examples of the related art and limitations relatedthereto are intended to be illustrative and not exclusive. Otherlimitations of the related art will become apparent to those of skill inthe art upon a reading of the specification and a study of the drawings.

SUMMARY

The following embodiments of the present invention and aspects thereofare described and illustrated in conjunction with systems, tools andmethods which are meant to be exemplary and illustrative, not limitingin scope. In various embodiments, one or more of the above-describedproblems have been reduced or eliminated, while other embodiments aredirected to other improvements to the existing art.

The present invention relates to a process and apparatus for treatingslurries of organic solids. A slurry of organic solids is admixed withhydrogen peroxide, followed by exposure to microwave irradiationresulting in the heating of the mixture and enhanced hydrolysis of theorganic solids. The treated slurry of organic solids can then be furthertreated in a variety of downstream processes, including solidseparation, digestion and fermentation. The supernatant portion of thetreated slurry of organic solids can subsequently be used beneficiallyas a source from which to recover valuable compounds such as nutrients(for example nitrogen, phosphate, potassium, magnesium, calcium) orindustrial organic compounds (such as acetic acid, propionic acid,butyric acid), or as a source of readily biodegradable organic compoundsfor supplementing a biological wastewater treatment process, digester orfermenter. The treatment process also results in the conversion of asignificant portion of volatile solids to soluble organic compounds,thus leaving reduced amounts of sludge solids for further treatment anddisposal and increasing the rate at which the waste can be stabilized indownstream treatment processes.

The process can also be used, for example, as a side stream process,treating a portion of return activated sludge in an activated sludgetreatment process. This would result in a significant reduction inoverall process sludge yield, and produce a supernatant stream suitablefor nutrient removal or recovery through a variety of known processes(chemical precipitation, ion exchange or struvite recovery for example).This would also provide a source of readily biodegradable organiccompounds, comprised primarily of volatile fatty acids (such as aceticacid, propionic acid and butyric acid) which can be used to improvebiological nutrient removal processes such as denitrification andenhanced biological phosphorus removal. Reintroduction of the treatedeffluent from the AOP at strategic points in a wastewater treatmentcould lead to significant improvements in denitrification rates as wellas biological phosphorus removal rates.

The term “slurry of organic solids” is used herein to refer generally towaste materials such as sewage sludge, animal manure, food processingwaste and the like. The term “supernatant” is used herein to refergenerally to a liquid wastewater solution separated from such a slurry,by means such as gravity sedimentation, floatation, filtration,centrifugation or the like.

Slurries to be treated using the current invention can have a suspendedsolids content in the range of 0.05% to 30%, while most typical slurriesthat are anticipated to be of commercial interest will typically havesuspended solids content in the range of 0.1 to 15%. Below this range ofsolids content the energy and chemical requirements are likely to becomeuneconomical, and above these solids ranges, the slurries becomedifficult to convey using fluid pumping equipment and efficient mixingof the oxidant in the slurry becomes difficult due to the elevatedviscosity of the slurry.

Peroxide dosage rates found to be effective in treating the slurries isa minimum of 0.03% H₂O₂ by volume in the admixed slurry, or 0.3 g ofH₂O₂ per litre of admixed slurry. Below this dosage rate the enhancementof thermal hydrolysis by microwave irradiation alone is notsignificantly improved. 30% hydrogen peroxide solution has been found tobe a suitable source of hydrogen peroxide for the process.

It has been shown that Ozone can be used in place of hydrogen peroxideas a source of oxidant for the current process, however in embodimentstested to date, hydrogen peroxide has been shown to be more effective.

For the treatment of secondary sewage sludge slurries, it has been foundthat pH adjustment is of some but little benefit to the process in termsof its ability to solubilize chemical oxygen demand, and reducesuspended solids levels. In this case operation in the pH range of 6 to7 has been found to be optimal.

For the treatment of certain slurries, such as dairy manure, it has beenfound that acidification of the slurry to a pH as low as 2, using astrong acid, such as sulfuric acid, either before or after treatmentwith the current invention significantly improves the solubilization ofthe slurry through acid hydrolysis.

Microwave irradiation at a frequency of 2450 MHz has been used to raisethe temperature of the admixed slurry at a rate of 5-50° C. per minuteto the target temperature, and thereafter maintain the temperature for aperiod of 0-15 minutes, and preferably 5 minutes.

Treatment temperatures in the microwave chamber of at least 50° C. arerequired to achieve effective solubilization of the slurry. Treatmenttemperatures up to 200° C. have been evaluated, and generally increasedtemperature results in increased solubilization for a given oxidantdose. It has also been found that the solubilization reaction isgenerally complete within a treatment time of 5 minutes in a batchreactor. Exposure to microwave radiation for longer periods of time wasnot found to improve the degree of solubilization of the slurries testedto date. Certain other types of slurries could however benefit fromlonger durations of treatment if they contain organic material that ismore resistant to oxidation and thermal hydrolysis.

In slurries tested to date, the current invention has been capable ofconverting up to 100% of the insoluble Chemical Oxygen Demand (“COD”),and phosphorus, to soluble COD, and ortho-phosphate respectively. At thesame time significant portions of total nitrogen are converted toammonia, and a large fraction of nutrients present in solid form areconverted to soluble form. The process also results in the destructionof up to 100% of volatile suspended solids.

The apparatus for carrying out the process could be either a batchprocess or a continuous flow process.

The batch process apparatus consists of a reaction vessel in whichorganic solid slurry is first introduced and mixed with hydrogenperoxide solution (either mixed in a common conduit before entering thereaction vessel, or introduced into the vessel through separate conduitsand mixed within the vessel. The admixed slurry is then irradiated withmicrowave energy as required to obtain the desired temperature profile.The contents of the vessel are then discharged using either a pump orthe pressure built up within the vessel. The contents can be passedthrough a heat exchanger to preheat the untreated slurry. Treated slurrycan then be further treated by solid/liquid separation before beingpassed on to further treatment or recovery processes.

The continuous flow process consists of admixing the organic solidslurry with hydrogen peroxide in a mixing vessel or conduit, and thenexposing the admixture to microwave irradiation in a flow through vesselor conduit enclosed within a microwave irradiation chamber.

The treated slurry is continuously pumped into the mixing vessel throughto the irradiation chamber and out. Once again, the treated waste can bepassed through a heat exchanger countercurrently with the fresh slurryof organic solids to preheat the slurry before it is introduced to themixing vessel. Treated slurry can then be further treated bysolid/liquid separation before being passed on to further treatment orrecovery processes.

Many processes could be used to further treat the treated slurry aftertreatment with the current invention. Because a large portion of the CODin the slurry has been converted to soluble form by the process, theremaining solids portion of the slurry contains a significantly reducednon-inert fraction. Further treatment of the solids fraction willtherefore result in relatively minor further breakdown of any remainingnon-inerts. It will therefore be beneficial in many cases to separatethe treated slurry into a solids containing fraction and a liquidfraction through solid-liquid separation using a variety of knownmethods.

The liquid fraction thus formed can then be treated in a variety ofavailable high rate anaerobic processes (such as fixed film bioreactors,upflow anaerobic sludge blanket reactors, hybrid suspended/attachedgrowth bioreactor) to generate biogas for recovery.

The elevated soluble nutrient content of the liquid fraction alsopresents an opportunity for nutrient recovery, through crystallizationof struvite, struvite analogs, calcium phosphate, or the like. Severalreactor designs for this purpose exist.

The liquid fraction also contains elevated concentrations of volatilefatty acids, (primarily acetic, propionic and butyric acids) which caneither be used directly in solution, or could be recovered throughdistillation, solvent extraction or other liquid/liquid separationprocesses.

In certain cases it may not be practical to separate the solid andliquid fractions of the treated slurry, but further treatment may stillbe desirable. In this case the soluble nature of the majority of theorganic compounds will allow such digestion or fermentation processes tobe designed with significantly reduced retention times. In some cases,the reduced solids content of the treated slurry may allow furthertreatment to occur in a fixed film bioreactor, upflow anaerobic sludgeblanket reactor, or hybrid suspended/attached growth bioreactor ratherthan a traditional fermenter or digester design.

In addition to the exemplary aspects and embodiments described above,further aspects and embodiments will become apparent by reference to thedrawings and by study of the following detailed descriptions.

BRIEF DESCRIPTION OF DRAWINGS

Exemplary embodiments are illustrated in referenced figures of thedrawings. It is intended that the embodiments and figures disclosedherein are to be considered illustrative rather than restrictive

FIG. 1 is a scematic diagram showing an apparatus embodying the presentinvention and a generalized process flow of treating a slurry of organicsolids according to the present invention.

FIG. 2 is a graph showing the effect of temperature and hydrogenperoxide dosage on percent soluble COD in a process of treating wasteactivated sludge from a municipal wastewater treatment plant accordingto the present invention.

DESCRIPTION

Throughout the following description specific details are set forth inorder to provide a more thorough understanding to persons skilled in theart. However, well known elements may not have been shown or describedin detail to avoid unnecessarily obscuring the disclosure. Accordingly,the description and drawings are to be regarded in an illustrative,rather than a restrictive, sense.

Hereinafter, preferred embodiments of the present invention aredescribed with reference to the accompanying drawings. However, thepresent invention is not limited thereto.

An apparatus according to the present invention and a process oftreating a slurry of organic solids with the apparatus is described.

FIG. 1 is a schematic diagram of an apparatus embodying the presentinvention and shows a generalized process flow for treating a slurrycomprising organic solids suspended in water with the apparatus.

As shown in FIG. 1, the microwave/hydrogen peroxide reactor system 1 andsolid-liquid separation tank 7 are arranged between further treatmentvessel 12 and slurry feed conduit 2.

Hydrogen peroxide solution storage tank 3 is connected tomicrowave/hydrogen peroxide reactor 1 via hydrogen peroxide solutionsupply conduit 5 and conduit 5 is equipped with pump 4 for supplyinghydrogen peroxide solution.

AOP reactor 1 is connected to solid-liquid separation tank 7 via conduit6.

Optional solid-liquid separation tank 7 is connected to furthertreatment vessel 12 via conduit 8 for feeding treated slurry of organicsolids. Solid-liquid separation tank 7 is also connected to optionalproduct recovery system 10 via conduit 9 for recovery of nutrients,minerals or organic compounds.

Product recovery system 10 is connected to further treatment vessel 12via conduit 19 for feeding the liquid fraction of the treated slurryafter recovery of nutrients, minerals or organic compounds. Conduit 11for recovered products (nutrients, minerals or organic compounds) or fordirect use of a portion of the liquid stream in conduit 9 is alsoconnected to product recovery system 10.

Further treatment vessel 12 is connected to solid-liquid separationsystem 14 via conduit 13 for drawing further treated slurry. Furthertreatment vessel 12 has vent 20 for recovery of biogas in the case ofanaerobic process.

Conduit 16 for dewatered solids and conduit 15 for liquid effluent areconnected to solid-liquid separation system 14. Conduit 16 canoptionally branch into two conduits; one, i.e. conduit 17, is fordisposing of residual solids, and the other, i.e. conduit 18 is forreturning solids to further treatment vessel 12.

Hereinafter, workings of the apparatus according to the presentembodiment are described.

Slurry comprising organic solids suspended in water is introduced intomicrowave/hydrogen peroxide reactor system 1 via conduit 2 and isadmixed with hydrogen peroxide and subsequently exposed to microwaveirradiation. Pump 4 works to supply hydrogen peroxide solution from thesolution storage tank 3 to microwave/hydrogen peroxide reactor system 1via conduit 5. The admixed slurry may preferably be treated for 5minutes for maintaining temperature within the range of 50 to 200 degreeCelsius. The combinations of hydrogen peroxide dosage amount and heatingtemperature vary depending on the target treatment results. Withtemperature lower than 50 degree Celsius, organic solids are notsufficiently disintegrated for enhancing solids solubilization to asatisfactory degree. Higher temperature or larger amount of hydrogenperoxide dosage has been shown to be unnecessary and uneconomical.

The slurry of organic solids treated by the microwave/hydrogen peroxidereactor system is then optionally sent to solid-liquid separation system7 via conduit 6 and separated into solids containing component and aliquid component. The solid containing component can then optionally besent to further treatment vessel 12 via conduit 8 and anaerobicallydigested by microorganisms. The supernatant rich in nutrients(phosphorus and nitrogen) is introduced into the crystallization reactor10 via conduit 9 for recovery. After recovery, the nutrient pellets(struvite or other phosphate compounds) are separated and harvested fromsupernatant via conduit 11. The remaining supernatant rich in solubleCOD is introduced into anaerobic digestion tank 12 via conduit 19.

The digested slurry of organic solids in anaerobic digestion tank 12 isdischarged from conduit 13 and separated into solid component and liquidcomponent in solid-liquid separation tank 14. The liquid component isdischarged from conduit 15 for wastewater and solid component isdischarged from conduit 16 for thickened solid waste. The solidcomponent in conduit 16 is discharged via conduit 17 for disposal. Ifdeemed necessary, part of the solid component is returned to anaerobicdigestion tank 12 through conduit 18 for further digestion. Meanwhile,the digester biogas in anaerobic digestion tank 12 is recovered fromvent 20.

With the above described treatment combination of hydrogen peroxide andmicrowave irradiation, organic solids are disintegrated to a high degree(up to 100 percent). Hydrogen peroxide is one of the most powerfuloxidizers. Through microwave irradiation, hydrogen peroxide can beconverted into highly reactive hydroxyl radicals that possess a higheroxidation potential than the hydrogen peroxide itself. Hardly solublesubstances in the slurry of organic solids, such as fibers and cellwalls, can be converted to readily biodegradable COD in the solubleform. This disintegration of organic solids can greatly enhance thebiological hydrolysis rate in anaerobic digestion process. As a result,the anaerobic digestion time could be shortened, digested biogas yieldcould have a significant increase, and solid waste to be finallydisposed could be reduced.

In addition, nutrients (phosphorus and nitrogen) in the slurry oforganic solids is efficiently released by the above described treatmentcombination of hydrogen peroxide and microwave irradiation. Phosphorusand nitrogen are converted and solubilized in the forms ofortho-phosphate and ammonia for direct recovery through crystallizationreactor. The nutrient pellet recovered in the forms of struvite,struvite analogs or other phosphate compounds is a valuable end-product.

According to the present invention, it is possible to treat a slurry oforganic solids in a cost-effective manner and to recover the energy andresource, i.e. digested biogas, soluble organic compounds and nutrientpellets.

In the present embodiment, AOP treated slurry of organic solids isintroduced to an anaerobic digestion tank. However, AOP treated slurryof organic solids may be introduced to a fermentation reactor. Thefermentation product, such as acetate, can be used as a substratematerial for many industrial applications.

It should be said that it will likely be familiar to someone skilled inthe art that:

-   -   further treatment vessel can be either a digestor, fermentor,        fixed film bioreactor, upflow anaerobic sludge blanket reactor,        or hybrid suspended/attached growth bioreactor. or other similar        known treatment processes    -   resource recovery can be solvent extraction, distillation, or        direct use in the case of organic compounds and crystallization        precipitation or ion exchange in the case of mineral compounds    -   other oxidants such as Ozone could be substituted for peroxide,        although perhaps with lesser effectiveness    -   various process configurations can be integrated with the        H₂O₂/microwave system (upstream and downstream process        configurations can vary significantly depending on local        conditions and the nature of the slurry being treated.)

EXAMPLE ONE

Secondary aerobic sludge was obtained from the pilot-plant wastewatertreatment facilities located at the University of British Columbia (UBC)campus. A set of twelve experiments were performed in order toinvestigate the effects of various hydrogen peroxide concentrations inthe MW/H₂O₂-AOP. Experiments were carried out at temperatures of 60, 80,100 and 120° C. Various concentrations of hydrogen peroxide were testedwith the objective of improving the degree of COD, nutrient and metalsolubilization from sewage sludge. Either 1 mL or 2 mL of hydrogenperoxide (30 wt %) was added to sludge to make up a total volume of 30mL for each microwave sample.

A closed-vessel microwave digestion system (Ethos TC DigestionLabstation 5000, Milestone Inc., U.S.A.) with a maximum output of 1000 Wwas used in this study. The system operates at 2450 MHz and consists ofdual independent magnetrons with a rotating microwave diffuser forhomogeneous microwave distribution. The microwave digestion system,using an independent system controller, provides real-time temperaturecontrol. The heating time was kept constant at 5 minutes for allexperiments at the pre-determined heating temperatures. The ramp timeswere varied with respect to temperature in order to maintain a uniformrate of heating (increase of ca. 20° C. per minute of heating) up to thedesired experimental temperatures.

FIG. 2 shows the percentage of soluble COD after treatments for the 3tested hydrogen peroxide concentrations (0, 1 and 2 mL) at fourtemperature settings (60. 80, 100 and 120° C.). The results showed thatfor each temperature, there was a significant increase in soluble CODwith increased hydrogen peroxide concentrations. At 60° C. and 2 mL ofH₂O₂ (i.e., 3 wt. % in sample of 30 mL), approximately 80% of the totalCOD was found to be in solution; this is almost 8 times of the amount ofsoluble COD from the control, where no hydrogen peroxide was added. Attemperatures of 80° C. and above, and at 2 mL of H₂O₂, approximately all100% of the COD was in soluble form.

As shown in FIG. 2, with the addition of H₂O₂, the accelerated releaseof COD into soluble form occurred at lower temperatures. For the 1 mLH₂O₂ addition runs, the maximum soluble COD was achieved at 100° C. Theincreased H₂O₂ addition allowed the maximum COD release to occur atlower microwave heating temperatures.

TABLE 1 and TABLE 2 list the soluble concentrations of nutrients, metalsand COD after AOP treatment. Ammonia concentrations ranged from 1.2-108mg N/L, while ortho-phosphate concentrations ranged from 27.5-75.6 mgP/L. The measured concentrations of soluble ammonia, ortho-phosphate,and magnesium were used to determine the Mg:NH3:PO4 molar ratio. Fromour results, ammonia was determined to be the limiting nutrient withoutany hydrogen peroxide addition in the microwave process. In all cases,magnesium was non-limiting, indicating for this treatment process thattheoretically, no magnesium addition is required for struvitecrystallization. Magnesium, calcium and potassium concentrations rangedfrom 18.3-40.0 mg/L, 9.9-31.2 mg/L, and 63.7-83.1 mg/L respectively.

TABLE 1 Temperature H2O2 Ortho-PO₄ NH₃ (° C.) (mL) (mg P/L) (% of TP)(mg N/L) (% of TN) 60 0 75.6 48.1 3.5 1.2 1 59.0 40.4 29.3 9.6 2 54.137.1 66.0 21.6 80 0 39.3 25.0 2.1 0.7 1 27.5 18.8 29.5 9.7 2 37.8 23.485.7 28.1 100 0 37.2 23.0 1.5 0.5 1 38.9 24.4 29.8 9.8 2 39.7 24.9 96.231.5 120 0 55.6 34.5 1.2 0.4 1 60.3 37.4 52.6 17.3 2 63.3 39.3 108 35.5

TABLE 2 Temperature H2O2 Metals (mg/L) Soluble COD (° C.) (mL) Mg Ca K(mg/L) (%) 60 0 23.2 14.8 66.3 390 9 1 19.5 14.3 73.5 2027 45 2 18.313.4 68.4 3532 79 80 0 19.0 10.3 72.7 566 13 1 13.1 6.8 59.6 2897 65 221.7 13.8 63.7 4668 105 100 0 29.8 16.2 75.4 812 18 1 29.0 20.6 69.03452 77 2 22.6 9.9 70.0 4650 104 120 0 29.4 23.1 83.1 2115 47 1 40.031.2 78.6 3207 72 2 34.8 29.4 72.0 4333 97

As described above, the process of the present invention, in whichmicrowave irradiation and hydrogen peroxide is combined, is highlyeffective not only in solubilization of carbon for acetate or methaneproduction, but also in solubilization of nutrients for crystallizationof fertilizer products, such as struvite.

While a number of exemplary aspects and embodiments have been discussedabove, those of skill in the art will recognize certain modifications,permutations, additions and sub-combinations thereof. It is thereforeintended that the following appended claims and claims hereafterintroduced are interpreted to include all such modifications,permutations, additions and sub-combinations as are within their truespirit and scope.

What is claimed is:
 1. A system for treating a slurry comprising organicsolids suspended in water, the system comprising: an inlet for receivingthe slurry; a reaction zone downstream from the inlet; one or moreperoxide injection ports at or upstream from the reaction zone, theperoxide ports connected to a supply of a peroxide-containing material;a microwave source disposed to irradiate the slurry in the reactionzone, producing treated slurry; and, an outlet for delivering thetreated slurry downstream from the reaction zone.
 2. A system accordingto claim 1 comprising a separation means connected to receive treatedslurry from the outlet, for separating treated slurry into a supernatantpart and a suspended solids-containing part.
 3. A system according toclaim 2 comprising a mineral crystallization means connected to receivethe supernatant part for crystallizing dissolved minerals from thesupernatant part.
 4. A system according to claim 3 wherein the mineralcrystallization means comprises a means for adding soluble ammonium ormagnesium to the supernatant part.
 5. A system according to any one ofclaims 1 to 4 comprising a further treatment means connected to receivethe suspended solids-containing part from the separation means, thefurther treatment means comprising means selected from the group of ananaerobic digester, a fermenter, an acidifier, a fixed film bioreactor,an upflow anaerobic sludge blanket reactor, a hybrid suspended/attachedgrowth bioreactor, and an acid hydrolysis reactor.